Preparation and functional properties of rice bran globulin‐chitooligosaccharide‐quercetin‐resveratrol covalent complex

Abstract BACKGROUND As the major protein (approximately 36%) in rice bran, globulin exhibits excellent foaming and emulsifying properties, endowing its useful application as a foaming and emulsifying agent in the food industry. However, the low water solubility restricts its commercial potential in industrial applications. The present study aimed to improve this protein's processing and functional properties. RESULTS A novel covalent complex was fabricated by a combination of the Maillard reaction and alkaline oxidation using rice bran globulin (RBG), chitooligosaccharide (C), quercetin (Que) and resveratrol (Res). The Maillard reaction improved the solubility, emulsifying and foaming properties of RBG. The resultant glycosylated protein was covalently bonded with quercetin and resveratrol to form a (RBG‐C)‐Que‐Res complex. (RBG‐C)‐Que‐Res exhibited higher thermal stability and antioxidant ability than the native protein, binary globulin‐chitooligosaccharide or ternary globulin‐chitooligosaccharide‐polyphenol (only containing quercetin or resveratrol) conjugates. (RBG‐C)‐Que‐Res exerted better cytoprotection against the generation of malondialdehyde and reactive oxygen species in HepG2 cells, which was associated with increased activities of antioxidative enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐Px) through upregulated genes SOD1, CAT, GPX1 (i.e. gene for glutathione peroxidase‐1), GCLM (i.e. gene for glutamate cysteine ligase modifier subunit), SLC1A11 (i.e. gene for solute carrier family 7, member 11) and SRXN1 (i.e. gene for sulfiredoxin‐1). The anti‐apoptotic effect of (RBG‐C)‐Que‐Res was confirmed by the downregulation of caspase‐3 and p53 and the upregulation of B‐cell lymphoma‐2 gene expression. CONCLUSION The present study highlights the potential of (RBG‐C)‐Que‐Res conjugates as functional ingredients in healthy foods. © 2024 Society of Chemical Industry.